although P3d is installed, the install program cannot find the path
Where, exactly, the screenshot you posted says it "cannot find the path" ?
It says it FOUND your P3D, but it's version 4.3, so it's too old, and since LFSB is a scenery 100% made in PBR, it simply cannot work in any P3D version lower than 4.4, even if we suggest using 4.5 HF2, which is the current release.